The present invention relates to an arrangement for rolling the frontal end of a deformable sleeve-shaped container jacket, comprising a supporting surface which radially supports the container jacket in the area of its end, also comprising, radially arranged to the supporting surface, a ring-shaped cavity having a closed bottom and an open top, which cavity has an essentially semicircular cross-section for acting axially on the end of the container jacket.
An arrangement of this type is prior art in European published patent 0 626 254. The cavity of the known arrangement comprises in circumferential direction a geometrically constant smooth surface, which, by means of axially pushing forward the frontal end of the deformable sleeve-shaped container jacket, effects the deforming process. Practical application has shown that a crease-free rolling of the frontal end of the container jacket by means of the above mentioned arrangement succeeds only when a lubricant, for example an oil, is used. There are, however, materials for the container jacket, for example certain types of paper, where the application of a lubricant is not desirable.
It is an object of the present invention, in the case of an arrangement of the above mentioned type, to realize the rolling of a frontal end of a container jacket without the use of any kind of lubricant.
This object has been achieved in accordance with the present invention in that the cavity is provided in the circumferential direction, at least in the transitional area between the supporting surface and the bottom, with a plurality of pocket-shaped recesses, between which rolling ridges, as part of the original cavity surface, remain.
In the embodiment according to the present invention, a closed rolling surface no longer acts on the frontal end of the container jacket, but rather a plurality of rolling ridges with larger or smaller widths. This causes the circulating line contact present in prior art to be interrupted according to the present invention, whereby the deformation forces during rolling are reduced by up to 40%. Even in the case of paper coated inside and outside, that is, in the case of thicker layers, no lubricant is necessary. Due to the reduced deformation forces, a coating of the rolling tool is also no longer necessary. Furthermore, because of the profiling of the arrangement according to the present invention, the setting accuracy during rolling can be lowered, whereby increased tolerances are permitted.
In the case of one variation, at least the cavity comprises a surface of plastic. Thus time-consuming re-working during the manufacture of deformation dies is superfluous. In addition, the use of plastic is a contributary factor to the omission of any kind of lubrication. It is, of course, possible to manufacture the whole arrangement out of plastic. Alternatively, in another embodiment, the arrangement can be made of another suitable material, for example aluminium.
The present invention has many varied applications. For example, the arrangement can be applied in the area of that end of the container jacket which is to form a flange around the edge of a container bottom to be inserted. Alternatively, the arrangement according to the present invention can be applied to the upper, open end of the container, in order, for example to produce a top lip, which may serve the attachment of a lid. In particular in the latter case, the rolling can take place in several stages with a plurality of similarly designed arrangements.
In one variation—based on a supporting surface supporting the container jacket on the inside—the cavity can be radially arranged on the outside. This variation serves in particular the formation of a lip which is rolled outwards, for example a top lip. The container jacket is hereby deflected outwards by the rolling ridges.
In a further variation—based on a supporting surface supporting the container jacket on the outside—the cavity can be radially attached inwards. This type of variation is used, for example, for forming a bottom flange of a container, whereby the container jacket is this time deflected inwards by means of the rolling ridges.
Depending on the particular application of the arrangement, the width of the recesses and the width of the rolling ridges can vary. In one case it can be purposeful when the width of the recesses correspond approximately to the width of the rolling ridges. In another case, it can be advantageous when the width of the recesses is several times the width of the rolling ridges. The pocket-like recesses themselves could extend out over the floor of the bottom and cover for example the entire cavity.
These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description thereof when taken in conjunction with the accompanying drawings wherein: